1. Field
Example embodiments relate to a method of forming a wiring including a carbon nanotube. More particularly, example embodiments relate to a method of forming a wiring including a carbon nanotube having reduced contact resistance.
2. Description of the Related Art
Semiconductor devices having high data transmission speed are desired for many applications. One way of increasing the data transmission speed of a semiconductor device may be to increase integration degree in device chips such that a chip includes a large number of cells. A design rule for wirings in semiconductor chips has been reduced to a nanometer scale to increase the integration degree of the cells. However, reducing the design rule of the wiring may cause some technical problems. For example, specific resistance of a wiring may exponentially increase depending on a decrease of a critical dimension of the wiring. Hillocks caused by electro-migration (which may increase the likelihood of cuts in the metal wiring) may occur. Formation of a diffusion barrier layer may become difficult in some applications. To overcome these problems, techniques for forming a wiring using a carbon nanotube have been investigated.
A carbon nanotube has a one-dimensional quantum-wire structure. The carbon nanotube also has electrical characteristics such as a quantum transport in one dimension. The carbon nanotube may have a good current density characteristic, as compared with a metal wiring. For example, it has been experimentally proven that the carbon nanotube may have a current density of about 109 A/cm2, and may exhibit ballistic transport characteristics.
There are some obstacles to the use of a carbon nanotube as a wiring of a semiconductor device. For example, the carbon nanotube may have poor adhesiveness to a metal and/or high contact resistance at an interface with a metal. The carbon nanotube has a relatively low specific resistance (e.g., at least about 1 μAcm), which may be lower than a specific resistance of copper. However, when contact resistance between the carbon nanotube and a metal is high, benefits and drawbacks of using the carbon nanotube may offset each other due to an overall increase in resistance. A carbon nanotube wiring has been widely researched by several companies (e.g., Infenion, Fujitsu, Samsung Electronics, etc).